Personality matters: Consistency of inter-individual variation in shyness-boldness across non-breeding and pre-breeding season despite a fall in general shyness levels in farmed American mink (Neovison vison)

Abstract

Individuals of the same species vary consistently in their behaviour across time and context, and this is often referred to as animal personality. In this study, we investigate animal personality based on the definition of personality traits as underlying dispositional factors, which are linked to biological internal factors that are stable and perhaps heritable. Although not directly measurable, these underlying dispositional factors predispose individuals to react through different behavioural patterns. We investigated the shyness-boldness continuum reflected in the consistency across time of the inter-individual variation in behavioural responses towards two different novelty tests: a novel object test representing non-social contexts and a mirror test representing social contexts. Our study animals were 60 farmed American mink (Neovison vison), which were raised in identical housing conditions. We recorded the approach behaviour of the mink towards novelty at two different times: the first time during non-breeding season in December 2013 and the second time during pre-breeding season in February 2014. Behavioural variables were analysed using principal component analyses and our results show consistency in inter-individual variation in shyness measures across seasons. This consistency differed across non-social and social contexts forming two different shyness-boldness dimensions as were also found across context in a previous study. To our knowledge this is the first study to reveal aspects of the shyness-boldness continuum across time and season in the American mink from non-breeding season in December to pre-breeding season in February. Our study confirms the existence of personality in farmed American mink, but interestingly, we saw a shift in the positioning of most individuals from shy to more bold on the shyness continuum when comparing the December measures to the February measures. This shift was further supported by the results of a simple stick test, which indicated a change towards a higher responsiveness towards humans in the pre-breeding season.